argument in form cannot contain nil or be empty Rails 4 - ruby-on-rails-4.1

Question

I have this First argument in form cannot contain nil or be empty issue with the form code of mine
i have defined in the controller as
class AdminController < ApplicationController
def new
#dashboard_user = DashboardUser.new
end
def create
#dashboard_user = DashboardUser.new(dashboard_params)
#dashboard_user.save!
end
def user_creation
end
private
def dashboard_params
params.require(:dashboard_user).permit(:user_name, :password, :last_name, :first_name, :middle_name , :phone)
end
end
and for the form
<%= form_for #dashboard_user, url: "/admin/user_creation", method: "post" do |f| %>
but i am getting this error is there anywhere i did a mistake or i overlooked some basic things?
P.S i am redirecting to the same page after the form has been submitted
routes.rb
Rails.application.routes.draw do
resources :admin, :only => [:create, :new] do
post 'user_creation', on: :collection
get 'user_creation', on: :collection
end
end
rake route
Prefix Verb URI Pattern Controller#Action
user_creation_admin_index POST /admin/user_creation(.:format) admin#user_creation
GET /admin/user_creation(.:format) admin#user_creation
admin_index POST /admin(.:format) admin#create
new_admin GET /admin/new(.:format) admin#new
root GET / admin#new

Answer 1

okay i got the answer i need to use the controller action that corresponds to the view that contains my form .. my form is user_creation so i need to create a function
def user_creation to make that work
def create
#dashboard_user = DashboardUser.new(dashboard_params)
#dashboard_user.save!
end
def user_creation
end
my view name is user_creation so changing the controller as below solved my issue
def create
end
def user_creation
#dashboard_user = DashboardUser.new(dashboard_params)
#dashboard_user.save!
end